It is known that a Streptomyces strain (NCIB 8845) or (ATCC No. 14,903) produces an antibiotic named Actinonin which exhibits antibacterial activity against gram-positive bacteria (U.S. Pat. No. 3,240,787). Some substances useful as the host defence stimulator or immunopotentiator are known, but there remains a need for a more effective agent useful for therapeutic, immunological treatment of in living animals bearing Ascites Sarcoma 180 tumor cells.
A further object of this invention is to provide a method for potentiating or stimulating the immune response in a living animal bearing Ascites Sarcoma 180 tumor cells. Other objects of this invention will be clear from the following descriptions.
From extensive researches, we, the present inventors, have found that such a substance which has an activity inhibitory to the enzymatic activity of an enzyme existing on the surfaces of organism cells have immunomodulating activities. And we have made researches in an attempt to find out such biologically active substances which are capable of enhancing the cellular or cell-mediated immunity, and as a result, we have now found that a substance which is produced by a microorganism having our laboratory designation Strain MG848-hF6 (an actinomycetes strain as isolated by us and stored in our laboratorys, the Institute of Microbial Chemistry, of Kami-Ohsaki, Shinagawa-ku, Tokyo, Japan) and which has been recovered by us and identified as an actinonin and given the following chemical structure: ##STR2## and a salt thereof have a remarkably high immunopotentiating acitivity in animals bearing Ascites Sarcoma 180 tumor cells. The actinonin obtained by us is in the form of colorless needles which show a melting point of 148.degree.-149.degree. C. and give a specific optical rotation [.alpha.].sub.D.sup.20 -50.degree. (c 2, ethanol). Based on this finding, we have accomplished this invention.
Actinonin as disclosed in literatures is known as a compound having antibacterial activity (see "I.A.M. Symposia on Microbiology" No. 6, "Chemistry of Microbial Product" pages 204-214 (1964) and U.S. Pat. No. 3,240,787). In these literatures, it is disclosed that actinonin has the following formula ##STR3## and shows physico-chemical properties, such as a melting point of 148.degree.-149.degree. C. and an [.alpha.].sub.D.sup.20 -53.9.degree. in ethanol and -65.0.degree. in water and that this actinonin exhibits an antibacterial activity. However, only through our recent researches, it has firstly been discovered by us that the compound of the formula (I) as obtained by us and identified as an actinonin exhibits pharmacological activities, particularly the activity of potentiating the cellular or cell-mediated immunity, namely the activity of enhancing or stimulating the immune response in a living animal bearing Ascites Sarcoma 180 tumor cells and is useful as a host defence stimulator for enhancing the immune response in a living animal bearing Ascites Sarcoma 180 tumor cells.